Effects of multiple oral dosing on IgE synthesis in mice: oral sensitization by albumin extracts from seeds of Jack fruit (Artocarpus integrifolia) containing lectins.

The IgE antibody response was studied in DBA/2 mice; the mice were pretreated orally with albumin extracts from seeds of Jack fruit (Jackalbumin) and subsequently immunized subcutaneously with Jackalbumin mixed with ovalbumin (OA) and a synthetic adjuvant, muramyl dipeptide (MDP). The allergenicity of Jackalbumin was evaluated by its capacity to induce a specific IgE response which was measured by passive cutaneous anaphylaxis (PCA) and by degranulation of washed peritoneal mast cells following antigen challenge (Jackalbumin or OA). Antibody against the crude extracts and anti-lectin (FIISP) IgE responses were also tested by PCA. After being fed eight doses of 1 mg Jackalbumin, DBA/2 mice became immunized: i.e. specific IgE antibody responses were observed and the peritoneal mast cells became sensitized. An increase in IgE response was verified in mice that were pre-fed and subsequently immunized. The results indicated that: the albumin extracts from Jack seeds, containing lectins, can be allergenic by the oral route; multiple oral doses with these extracts can induce an enhancement of the IgE response on subsequent subcutaneous immunization; antigenically, Jackalbumin does not seem to cross-react with OA; the lectins contained in the albumin fraction from Artocarpus seeds were also shown to be allergenic; the IgE titres showed an inverse correlation to the degree of purification of the lectin used for PCA challenge.